Field of the Invention
There is a demand in many fields of activity for small lightweight flashing indicators, safety devices, to be carried by personnel and to provide visual contact or location in dark areas. Such applications include firemen, police, guards, haz mat teams, inspectors, divers, military, covers, ski patrols, refineries, mining, warehousing and others. Such safety devices use flashing bright lights, such as L.E.D.'s and also utilize certain intense colors such as reds and oranges which penetrate darkness, smoke and water. Many such devices are available and are incorporated in what are known as personal alert safety systems (designated PASS). The aforementioned U.S. Pat. No. 5,317,305 is an excellent example of a PASS device using flashing indicator lights and includes information about other safety devices which have flashing indicators.
The known visual indicators use single periodically flashing light sources, usually with lens buttons of colored plastic, but none of the known devices include what I have designated a light emission multiplier in front of the light source or sources. This invention involves discovery of a light emission multiplying principle utilizing a thin synthetic plastic sheet with an array of micro prisms on one side of the sheet, the other side of the sheet being smooth, and such sheet being used as a lens array spaced a short distance from a small concentrated bright light source, which can be a bright visual light source or a light source in the invisible spectrum, e.g., near infrared and infrared spectrum. The sheet of micro prisms is disposed so the smooth side faces the light source and the side which contains the microprisms is facing away from the light source. It is intended that the phrases, light and light source, as used herein, include visible and invisible light. Such sheets of an array of microprisms are currently made and are available on the market, being manufactured by the Reflexite R Corporation, having offices in Avon, Connecticut and other places. The sheets of microprisms are used for retroreflective purposes on various guard devices, safety belts and barriers, but have never been used or proposed for use as light emission multipliers as a lens array in front of a light source. The micro prisms are very small, and can be made almost invisible to the naked eye, being measured in millionths of an inch.
Patents pertaining to the retroreflective sheets with micro prism arrays and the method and apparatus for making such material among others are as follows: U.S. Pat. No. 3,684,348 on Retroreflective Material; U.S. Pat. No. 3,689,346 on Method for Producing Retroreflective Material; and U.S. No. 3,935,359 on Retroreflective Sheeting and Method and Apparatus for Producing Same. The inventor of each of the above-identified patents is the same, William P. Rowland.
Prior art on L.E.D. devices used with diffusers of the emitted light can be found in the following patents, none of which teach use of L.E.D.'S with a lens sheet with a microprism array to provide multiplication of the light emission from the L.E.D.: U.S. Pat. No. 3,786,499 to ALFRED S. JANKOWSKI on ALPHANUMERIC DISPLAY PACKAGE; U.S. Pat. No. 3,810,168 to R. NISHINA on LUMINOUS DISPLAY PANEL WITH SEGMENT MATRIX & DIFFUSER; U.S. Pat. No. 3,911,430 to ALFRED S. JANKOWSKI et al on ALPHA-NUMERIC DISPLAY PACKAGE; 3,918,053 to H. TOWNE et al on DIGITAL DISPLAY; U.S. Pat. No. 4,191,943 to BRUCE CAIRNS et al on FILLER-IN-PLASTIC LIGHT-SCATTERING COVER; and U.S. Pat. No. 5,140,220 to Y. HASEGAWA on LIGHT DIFFUSION TYPE LIGHT EMITTING DIODE.